System of electric heating.



T. VAN ALLER.

SYSTEM OF ELECTRIC HEATING.

APPLICATION FILED MAYH. 1918.

1,282,330. Patented Oct. 22, 1918.

Inventor- THChO Van Al Ier,

bg His Attorney.

UNITED STATES PATENT- OFFICE- 'TYCIIO VAN ALLER,

OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACORPORATION OF YORK.

SYSTEM or ELECTRIC HEA I'NG.

State of New-York, have invented certaln new and useful Improvements inSystems of Electric Heating, of which the following is a specification.

My invention relates to a system of electric heating. so arranged that avariety of degrees of heat may be obtained, andv it has for its objectthe improvement in a system of this character.

Heretofore, so far asI am aware, difi'erent degrees of heat in anelectric heating device have been secured either by the use of anexternal resistance, or by the use of two distinct heating elementshaving a switch associated therewith and so arranged as to connect thetwo elements in series to the supply circuit for low heat and to connectthe two elements in multiple for high heat. The first system involvingthe use of an external resistance is, of course, wasteful of energy. Thesecond system as stated, involves the use of two distinct heatingelements and to that extent increases the cost of the device.Furthermore, the ratios of heat obtained by connecting two equalresistances in series and in parallel are as one to four. respectively,and this ratio is not always the most desirable in practice.

In accordance with my invention, an electrically continuous heatingelement is provided to which intermediate terminals are connected insuch a manner as to divide the resistance element into different numbersof substantially equal parts, with associated means for connectingthe'parts of the element formed by either system ofdivision to thesupply circuit in multiple, thereby ob- ,taining diflerent heatcapacities.- At the same time all parts of the resis ance element carrythe same amount of current at any given time, thus tending to produce alonglife in the heating element.

For a better understanding of my invention, reference may be had to theaccompanying drawing in which Figure 1 is a perspective view, partiallybroken away, of a heating device associated with my invention; Fig. 2 isa diagram of the connections and Fig. 3 is a diagram illustrating theheatingelement and the terminals therefor.

Specification 01' Letters Patent.

Patented Oct. 22, 1918.

Application filed May 11, 1918. Serial No, 233,825.

Referring now to the drawings, 10 is a refractory tube forming a part ofan electric furnace in connection with which I have here illustrated myinvention. An electrically continuous resistance element 11 is woundaround the tube and is provided with end terminals 12 and 13 and withintermediate terminals, here illustrated as three, 14, 15 and 16,dividing the resistance element into sections 11, 11, 11 and 11, theterminal 14 dividing the element into two equal parts, the one part madeup of the sections 11 and 11 and the other part made up of the' sections11 and 11, while the terminals 15 and 16 divide the resistance elementinto three equal parts, one part ,being the section 11, another partmade up of the sections 11 and 11 and the third part coinciding with thesection 11 If the resistance element is wound beginning at the left asviewed in Fig. 1, a length of wire is left projecting from the tubesufficient to form the terminals 13, and the section 11 is wound, theother end of the section being brought out away from the tube andtwisted together with or otherwise secured to. the projecting end of theadjacent section 11 to form the terminal 15. In Fig. 1 the wires 13 and12 are the terminals, the other wires there shown being thecontinuations of wires that are wound around the tube 10 as supports.The remaining sections are wound similarly to the section 11. In thismanner a single electrically continuous resistance unit is provided, theterminals of which are continuous with the resistance members of thevarious sections and may be carried to points sufliciently remote fromthe heating device itselfto prevent their becoming overheated at thepoints where they are connected to the supply conductors. Forconvenience the terminals in Fig. 2 are indibeing connected to thesupply conductor 22.

When the switch is moved to the left as viewed in Fig. 2, the arms 19,20 and 21 engage stationary contacts 24:,25 and 26, respectively, andwhen it is moved to the right,

they engage contacts 27 28 and 29. The contacts 24 and 25 are connectedto the terminals 15 and 16, respectively, and the terminals 26' and 27are connected together and are connected to the terminal 12 and are alsopreferably connected through a pilot light to the supply conductor 22. The contact 28 is a blank contact and the contact 29 is connected to theresistance element 14 and hence to the middle of the entire resistanceelement. The supply conductor 22 is connected to the terminal 13.

It will be apparent that when the switch is moved to the ri ht, the twoparts of the resistance element etween the terminals 12 and 14, and 13and 14, respectively, are connected to the supply conductors 22 and 23in multiple, and when the switch is moved to the position at the left,as viewed in Fig. 2, the three parts formed between the terminals 13 and16-, 16 and 15, and 15 and 12 are connected to the supply conductors 22and 23 in multiple. These ratios of heat are substantially as 1:2 and Ihave found that this ratio is particularly desirable for certainclasses'of work and particularly for i furnaces where it is desirable toutilize the high. heat in raising the furnace to the desired temperatureand then operating the same at a heat which is substantially half thatof the high heat.

In order further to vary the amount of heat that may be obtained in theheating device, I have shown the supply conductors 22 and 23 connectedto two different supply circuits of different voltages vthrough a switchB.- Different voltages are assumed to exist between the lines 31 and 32,and 31 and 33. For instance, the voltage between the lines 31 and 33 maybe 125 and that between 31 and 32 may be 250. By moving the switch B tothe right or to the left, either of these voltages is impressed on thesupply conductors 22 23 and still further variations in the heatingelement thereby obtained.

It will be apparent that the pilot light 30 is connected in circuit whenthe switch A is thrown to the high heat position.

It will be apparent that under all conditions of operation, the parts ofthe resistance element carry the same amount of cur-.

rent thereby tending to increase the life of the resistance element.

While I have herein shown and described one modification of myinvention, I do not desire tobe limited to the exact arrangement shownand described but seek to cover in the appended claims all thosemodifications which come within the true spirit and scope of myinvention.

hat I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In combination, an electric heating device comprising an electricallycontinuous resistance element, intermediate terminals dividing theelement into differing numbers of substantially equal parts, a supplycircuit, and means for connecting the parts of the resistance elementformed according to either division to the supply circuit in mul-'tiple.

parts of the resistance element formed in accordance with eitherdivision to the supply circuit in multiple.

3. In combination, an electric heating de vice comprising anelectrically continuous resistance element, intermediate terminalsformed as continuations of the resistance element and dividing theelement into differing numbers of substantially equal parts, a supplycircuit, and means for connecting the parts of the resistance elementmade according to either division to the supply circuit in multiple.

4. In combination, a hollow electric heating device, an electricallycontinuous resistance element wound around the same, intermediateterminals dividing the element into differing numbers of substantiallyequal parts, a supply circuit, and means for connecting the parts formedby either division to the supply circuit in multiple.

In witness whereof, I have hereunto set my hand this 9th dgy of Mary,1918.

, T CHO AN ALLER.

